90 



CHLOROPHYCEAE 



possess a bilateral branching system. The genus has been divided 

 by Borgesen into three groups : 



(a) The species of this group, which grow where there is much 

 mud, possess rhizomes that are vertical or oblique, thus enabling 

 them to reach the surface even when covered successively by mud 

 (e.g. C. 'verticillata). 



(b) The rhizome in these species first branches at some distance 

 from its point of origin and it possesses a pointed apex which aids 

 in boring through sand or mud (e.g. C. cupressoides). 



{c) The rhizome is richly branched immediately from its point 

 of origin and the various species are principally to be found attached 

 to rocks and coral reefs (e.g. C. racemosa). 



Fig. 62. Caulerpa. A, B, C prolifera ( x ^). C, C. racemosa f. macrophysa ( x ^). 

 D, E, C. sertularioides, side branches ( x ^). F, C. crassifolia f. mexicana ( x ^). 

 G, structure of wall and two skeletal strands, H, longitudinal section of aerial 

 portion showing longitudinal (Z) and transverse {i) support strands. I, transverse 

 section of rhizome with skeletal strands. J, K, L, C. prolifera, reproductive 

 papillae ( x 5). M, C. prolifera with gametes being liberated. (A-F, after Taylor; 

 G-I, after Fritsch; J-M, after Dostal.) 



It has also been shown that the form of the thallus in some of 

 the species is largely dependent upon the conditions of the habitat, 

 a feature particularly well illustrated by the plastic C cupressoides 

 and C. racemosa: 



(i) In exposed situations the plants are small and stoutly 

 built. 



